When using the communicate function in netFORUM, an email address will automatically populate in the From drop-down according to the user's profile. If the user does not have an email address in his or her user profile, no email address will populate, and the user will not be able to use the communicate function.
The user's profile shows an email address. After making this change, make sure to clear cache and Populate User Privileges.
If you need to send an email on behalf of a different e-mail address (for example, you need to send an email from a generic account like announcements@zzzz.org or from the association president), then you'll need to add an Email Alias to the user. Email Aliases are added from the User page in the Admin module.
When netFORUM delivers the message, it adds a Reply-To and a Return-Path attribute to the message header with the value of the selected reply to email address. Most mail servers use the Return-Path as the address to send bounces and for other purposes. The Reply-To is used by mail clients to send a message when a user chooses the reply option in the mail client.